The purpose of this project is to biochemically and immunologically characterize type C RNA viruses in order to understand the mechanisms by which these viruses transform cells. Another goal of this research is to determine whether or not these viruses play a role in the etiology of human cancers. Studies currently in progress are the following: 1) Biochemical characterization of mammalian transforming viruses; 2) Biochemical characterization of new isolates of type C viruses; 3) Studies of the cellular control of endogenous viral gene expression in normal and malignant cells; 4) Search for the presence of type C viral genes and gene products in human tumors.